package demo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {

    private DatagramSocket socket=null;

    public UdpEchoServer(int port) throws SocketException {
        socket=new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动！");
        while (true){
            //1、创建数据报
            DatagramPacket requestPacket=new DatagramPacket(new byte[4096],4096);
            //2、接收并解析数据报
            socket.receive(requestPacket);
            String request=new String(requestPacket.getData(),0,requestPacket.getLength());
            //3、计算响应并返回给客户端
            String response=process(request);
            DatagramPacket responsePacket=new DatagramPacket(response.getBytes(), response.getBytes().length,requestPacket.getSocketAddress());
            socket.send(responsePacket);
            //4、打印日志记录此次数据交互的详情
            System.out.printf("[%s:%d] req=%s resp=%s\n",requestPacket.getAddress().toString(),requestPacket.getPort(),request,response);
        }
    }

    public String process(String request){
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server=new UdpEchoServer(9090);
        server.start();
    }
}













